This invention relates to a resin encapsulation type semiconductor device by use of an epoxy resin composition, more particularly to a resin encapsulation type semiconductor device by use of an epoxy resin composition which can give a cured product of high reliability.
Epoxy resin compositions have frequently been used for encapsulation of semiconductor elements or electrical circuits in integrated circuit (IC), large scale integrated circuits (LSI), transistor, etc., or other parts.
For epoxy resin composition to be used for such parts of high performance, high reliability is increasingly demanded as the semiconductor devices of today are enlarged in scale and increased in density. Particularly, among high reliabilities, improvement of thermal cycle resistance has been strongly desired.
To explain about the thermal cycle resistance as mentioned here, an epoxy resin composition for encapsulation should never give damages to the parts encapsulated therein depending on the temperature change in the environment. The extent of difficulty in giving such damages is evaluated as the thermal cycle resistance.
To illustrate in detail by referring to an example of a resin encapsulation type semiconductor device, as shown in FIG. 1, 1 is a semiconductor element, which semiconductor element 1 is mounted on a bed 2. The electrode portions (pad portions) of the above semiconductor element 1 are connected with a pluralilty of bonding wires 3, and the other ends of these wires are connected to the lead pin 4.
And, the above semiconductor element 1, the bed 2, the wire 3 and some parts of the lead pin 4 are encapsualted with a resinous encapsulating material 5. Accordingly, these encapsulated parts are subject to mechanical stress by the resinous encapsulating material 5. Due to difference in coefficient of thermal expansion between the resinous encapsulating material 5 and the parts encapsulated therein, when the resin encapsulation type semiconductor device is exposed repeatedly to high temperature and low temperature, it can no longer stand the stress due to difference in coefficient of thermal expansion, until the bonding wires 3 may disadvantageously be broken or cause poor contact.
As the epoxy resin composition for encapsulation, a composition comprising an epoxy resin, a curing agent, an amine type curing accelerator such as imidazole, a halide and antimony trioxide has been proposed. The composition according to this proposal lacks humidity resistant reliability, because it gives damages such as aluminum electrode corrosion to the parts encapsulated therein, and is unsuitable particularly for encapsulation of parts of high performance such as LSI.
Japanese Patent Publication No. 60779/1982 discloses an epoxy resin composition for encapsulation of semiconductor devices, comprising an epoxy resin, a curing agent, an organic phosphine curing accelerator, a halide and antimony trioxide. The composition according to this disclosure has enhanced humidity resistant reliability to a great extent by use of an organic phosphine curing accelerator in place of an amine type curing accelerator such as imidazole. However, with respect to various characteristics other than humidity resistant reliability, the thermal cycle resistance proved to be insufficient.
Japanese Patent Publication No. 32506/1982 discloses a flame retardant epoxy resin composition comprising an epoxy resin, a curing agent, an imidazole curing accelerator and diantimony tetroxide and hexaantimony tridecaoxide. The composition according to this disclosure is intended to improve humidity resistant reliability by formulation of diantimony tetroxide and hexaantimony tridecaoxide in the conventional composition containing imidazole curing accelerator. However, as apparently seen from the fact that no significant difference can be exhibited with respect to the thermal cycle resistance in the respective compositions obtained by formulating diantimony trioxide and diantimony tetroxide, respectively, with imidazole curing accelerator, such a composition failed to give no improvement of the thermal cycle resistance at all.
Japanese Patent Publication No. 33125/1984 discloses an epoxy resin composition for encapsulation of semiconductor devices, comprising an epoxy resin, a curing agent, an organic phosphine curing accelerator, a halide and antimony trioxide. Although, in the specification, the above antimony trioxide is not described clearly as antimony trioxide but is described merely as an antimony oxide, the term "an antimony oxide" used herein is believed to surely mean antimony trioxide, as is apparent to the skilled in the art. The composition according to this disclosure also did not show sufficient thermal cycle resistance.